Determining the sire fertility of lost Y-Chromosome lineage in Holsteins
Open Access
- Author:
- Jenkins, Kendal
- Area of Honors:
- Animal Sciences
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Chad Daniel Dechow, Thesis Supervisor
Wansheng Liu, Thesis Honors Advisor - Keywords:
- Genetic Conservation
Sire Fertility
Calving
Genetic Conservation
Genetic Conservation
Sire Fertility
Calving
Sire Fertility
Calving - Abstract:
- The modern Holstein (HO) breed has been reduced to two Y-chromosome lineages due to selection since the introduction of artificial insemination. The objective of this study is to contrast sire fertility, calving ease (CE), stillbirths (SB), and birth weight of modern HO sires, Angus sires, and sires from Y-chromosome lineages lost since the 1960s (lost-Y). The lost-Y lineages were recently reconstituted by mating historic bulls with semen available from the USDA National Animal Germplasm Program (NAGP) repository to modern HO dams. Breeding and calving records from one California herd, one New Mexico herd, one Pennsylvania herd, and the Penn State dairy herd were retrieved from herd management records. Records were retained from all cows bred during the time-period the lost-Y semen was used on the respective farms, with 11,132 observations (8140 modern HO, 2435 Angus, and 557 lost-Y) for conception rate. Calving records included 2941 SB observations, 2921 CE observations, and 1433 birth weight observations. Conception rate was evaluated with the HPMIXED procedure of SAS with fixed effects of lineage (modern HO, Angus, lost-Y), insemination number, and herd-year. Random effects were cow, sire, and herd-year-month of insemination. Models for calving traits included fixed herd-year, lineage (modern HO, Angus, lost-Y), and sex. The conception rate Least-Squares-Means (LSM) for lost-Y (42.30% ± 4.14) was not different (P>0.05) from Angus (36.06% ± 2.56) and modern HO (40.22% ± 1.45). Lost-Y SB (4.89% ± 1.51) was not significantly different from Angus (4.153% ± 1.29) or modern HO (4.28% ± 1.09). LSM for lost-Y CE (1.38 ± 0.05) was higher (P<0.01) than Angus (1.20 ± 0.04) and modern HO (1.23 ± 0.02), likely due to higher (P<0.01) lost-Y birth weight (44.67kg ± 1.04) compared to Angus (41.40kg ± 1.04) and modern HO (41.52 ± 0.42). This research suggests that the loss of Y-chromosome lineages since the introduction of artificial insemination was not due to repressed sire fertility, and that calves from these particular lost-Y lines weighed more at birth. Results suggest that semen from older sires in the germplasm collection of NAGP can be utilized with little or no detrimental effects.